01 - 
                Set your oven to 375°F (190°C). Put parchment paper on a baking tray.
              
              
              
                02 - 
                Grab a big bowl and throw in the beef, breadcrumbs, milk, egg, onion, garlic, salt, pepper, and Worcestershire sauce. Mix everything really well.
              
              
              
                03 - 
                Take some of the mix, make it flat, put cheese in the middle, and roll it into a ball. Do this with all the meat mixture.
              
              
              
                04 - 
                In a small bowl, stir together the ketchup and mustard. Brush this all over your meat balls.
              
              
              
                05 - 
                Pop them in the oven for 25-30 minutes until they're done and the tops look golden brown. Sprinkle parsley on top.